AD7862ARSZ-2 Datasheet, PDF (1/16 Pages) Analog Devices – Simultaneous Sampling Dual 250 kSPS 12-Bit ADC

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Simultaneous Sampling
Dual 250 kSPS 12-Bit ADC
AD7862
FEATURES
Two Fast 12-Bit ADCs
Four Input Channels
Simultaneous Sampling & Conversion
4 ␮s Throughput Time
Single Supply Operation
Selection of Input Ranges:
؎10 V for AD7862-10
؎2.5 V for AD7862-3
0 V to 2.5 V for AD7862-2
High Speed Parallel Interface
Low Power, 60 mW typ
Power Saving Mode, 50 ␮W typ
Overvoltage Protection on Analog Inputs
14-Bit Pin Compatible Upgrade (AD7863)
APPLICATIONS
AC Motor Control
Uninterrupted Power Supplies
Data Acquisition Systems
Communications
GENERAL DESCRIPTION
The AD7862 is a high speed, low power, dual 12-bit A/D
converter that operates from a single +5 V supply. The part
contains two 4 µs successive approximation ADCs, two track/
hold amplifiers, an internal +2.5 V reference and a high speed
parallel interface. There are four analog inputs that are grouped
into two channels (A & B) selected by the A0 input. Each
channel has two inputs (V_A1 & V_A2 or V_B1 & V_B2) that can be
sampled and converted simultaneously thus preserving the
relative phase information of the signals on both analog inputs.
The part accepts an analog input range of ± 10 V (AD7862-10),
± 2.5 V (AD7862-3) and 0–2.5 V (AD7862-2). Overvoltage
protection on the analog inputs for the part allows the input
voltage to go to ± 17 V, ± 7 V or +7 V, respectively, without
causing damage.
A single conversion start signal (CONVST) places both track/
holds into hold simultaneously and initiates conversion on both
inputs. The BUSY signal indicates the end of conversion, and
at this time the conversion results for both channels are avail-
able to be read. The first read after a conversion accesses the
result from V_A1 or V_B1, while the second read accesses the result
from V_A2 or V_B2, depending on whether the multiplexer select
A0 is low or high, respectively. Data is read from the part via a
12-bit parallel data bus with standard CS and RD signals.
In addition to the traditional dc accuracy specifications such as
linearity, full-scale and offset errors, the part is also specified for
dynamic performance parameters including harmonic distortion
and signal-to-noise ratio.
FUNCTIONAL BLOCK DIAGRAM
VREF
2kΩ
VDD
+2.5V
REFERENCE
AD7862
VA1
SIGNAL
SCALING
MUX
VB1
SIGNAL
SCALING
VA2
SIGNAL
SCALING
MUX
VB2
SIGNAL
SCALING
TRACK/
HOLD
12-BIT
ADC
TRACK/
HOLD
12-BIT
ADC
OUTPUT
LATCH
CONVERSION
CONTROL LOGIC
CLOCK
DB0
DB11
CS
RD
A0 BUSY CONVST
AGND AGND DGND
The AD7862 is fabricated in Analog Devices’ Linear Compat-
ible CMOS (LC²MOS) process, a mixed technology process
that combines precision bipolar circuits with low power CMOS
logic. It is available in 28-lead SSOP, SOIC and DIP.
PRODUCT HIGHLIGHTS
1. The AD7862 features two complete ADC functions allowing
simultaneous sampling and conversion of two channels. Each
ADC has a 2-channel input mux. The conversion result for
both channels is available 3.6 µs after initiating conversion.
2. The AD7862 operates from a single +5 V supply and
consumes 60 mW typ. The automatic power-down mode,
where the part goes into power down once conversion is
complete and “wakes up” before the next conversion cycle,
makes the AD7862 ideal for battery-powered or portable
applications.
3. The part offers a high speed parallel interface for easy con-
nection to microprocessors, microcontrollers and digital
signal processors.
4. The part is offered in three versions with different analog
input ranges. The AD7862-10 offers the standard industrial
input range of ± 10 V; the AD7862-3 offers the common
signal processing input range of ±2.5 V; while the AD7862-2
can be used in unipolar 0 V – +2.5 V applications.
5. The part features very tight aperture delay matching between
the two input sample-and-hold amplifiers.
REV. 0
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© Analog Devices, Inc., 1996